Project abstract Over 2.2 million US adults have an intellectual or developmental disability (IDD), and experience disparities in economic standing, health, and education. In the past twenty years, more young people are carrying IDD diagnoses (5.8% of children age 3-17, 35% increase since 1999). As this population enters the reproductive period, individuals, families, and researchers have raised concern about wellbeing during pregnancy and parenthood for women with IDD and their children. It is vital to understand the current proportion of pregnancies; risk factors for poor pregnancy outcomes; and resulting maternal and child developmental outcomes and familial service use in women with IDD to adequately serve the population with IDD and prepare for future, larger cohorts exercising their reproductive rights. We aim to build the foundational knowledge necessary to improve pregnancy outcomes and develop programs to support parents with IDD. In this R03, we propose to leverage the Big Data 4 Little Kids (BD4LK) project which links Wisconsin State Medicaid for all pregnancies from 2007-2016 (N?260 000) to one-year prepregnancy Medicaid claims, post-partum maternal claims and health service use, and child health outcomes and health service use. Medicaid is the leading health service provider for people with IDD in Wisconsin;6 yet, these data are underutilized to examine reproductive and pregnancy related health outcomes service use. Our three aims are to: (1) Estimate proportion of live births, and calculate age specific and total fertility rate in women with IDD in our BD4LK sample, comparing results to mothers without IDD; (2) Evaluate whether pregnant women with IDD are at greater risk for maternal pregnancy or child related complications compared to pregnant women without IDD and investigate potential pathways; and (3) Characterize post-pregnancy outcomes for mothers with IDD and their children including health outcomes and health service uptake and compare with outcomes for mothers without IDD. This approach is innovative for its use of this unique data set, methodologically sound approach, and interaction with women with IDD in the research process. Our results will help service providers better serve women with IDD of reproductive age and their families. Results will also help us identify specific areas for medical and behavioral intervention. As larger cohorts of individuals with IDD age and their reproductive rights are recognized, we will see more parents with IDD.7-10 This grant will provide the preliminary data and resources needed to support further data linkages to assess social service use. Additionally, this work will support our aim to build a prospective longitudinal cohort of women with IDD and their families that can be leveraged to study outcomes and service use and develop effective interventions to improve health and quality of life for this growing population of parents with IDD and their children.